It's not possible to enable it for the rtc_base_approved
target but since a larger refactoring is ongoing for webrtc/base
this CL doesn't attempt to fix that.
Changes made:
* Move webrtc/system_wrappers/include/stringize_macros.h into
webrtc/base:rtc_base_approved_unittests (and corresponding
unit test to rtc_base_approved_unittests).
* Move md5digest.* from rtc_base_approved to rtc_base_test_utils target.
* Move webrtc/system_wrappers/include/stringize_macros.h (+test) into
webrtc/base.
* Remove unused use include of webrtc/base/fileutils.h in
webrtc/base/pathutils.cc
BUG=webrtc:6828, webrtc:3806, webrtc:7480
NOTRY=True
Review-Url: https://codereview.webrtc.org/2717083002
Cr-Commit-Position: refs/heads/master@{#17766}
